A suspected chemical attack in rebel-held northwestern Syria killed dozens of civilians including children and left many more sick and gasping, causing international outrage Wednesday. The attack on the town of Khan Sheikhun killed at least 58 civilians and saw dozens suffer respiratory problems and symptoms including vomiting, fainting and foaming at the mouth, the Syrian Observatory for Human Rights monitoring group said.

Syria's opposition blamed President Bashar al-Assad's forces, saying the attack cast doubt on the future of peace talks. The army denied any involvement in a statement blaming "terrorist groups" for using "chemical and toxic substances".